Selecting finger arrangement including damping means for use in crossbar switches



Dec. 28, 1965 s. KOBUS 3,226,518

SELECTING FINGER ARRANGEMENT INCLUDING DAMPING MEANS FOR USE IN CBOSSBAR SWITCHES Filed June 25, 1963 F/G/ F/G4.

y Inue or STAMSLAS KbBus Attorney United States Patent SELECTENG FINGER ARRANGEMENT INELUD- ING DAMPING MEANS FUR USE IN CROSSBAR SWITCHES Stanislas Kobus, Paris, France, assignor to International Standard Electric Corporation, New Yorir, N.Y., a corporation of Delaware Filed June 25, 1963, Ser. No. 290,468 Claims priority, application France, July 5, 1962,

8 Claims. (Cl. 200-166) The present invention relates to improvements to crossbar switches and more particularly to selecting fingers used in such switches.

In a multiselector, a selecting bar is operated first to prepare the connection of a selector to a predetermined line. This connection is established by the operation of a holding armature of the selector. The selecting bar bears small fiexible metallic wires called selecting fingers which interpose between the holding armatures and the operating cards that drive the contact springs. A single bar includes one selecting finger per selector.

When a connection is established, a selecting finger is trapped between an operating card and a holding armature but since the selecting finger is flexible, the selecting bar can nonetheless be restored to rest position.

To obtain s ufiicient flexibility the selecting fingers generally are composed of a steel wire terminated in a helical spring. The fingers are fixed to the selecting bar by means of the spring end. By this means suitable selecting digit flexibility is obtained but the elasticity also presents a potential problem. If no precautions are taken, the operation of a bar or the release of a connection are followed by prolonged vibration of selecting fingers. If the control of another connection is effected in the next instant, not only the required connection but also the connection to one of the levels wherein a selecting finger still vibrates sufficiently to come to selection position is initiated.

In order to avoid this drawback, there has been provided in most of the existing systems a selecting finger damper. It is a metallic piece loosely attached where the selecting finger wire starts the first spire of the helical spring. The metallic piece is terminated by a ring through which passes the selecting finger wire in order that the energy normally dissipated in vibrations will be shock-absorbed. This device is satisfactory, though the damping is not total, brief oscillations still subsist.

However, the introduction of new electronic techniques in automatic switch control circuits raises the problem again because of the increased speed of operation required. Indeed, the operating speed of these circuits is such that the call routing rate is only limited by the operating rate that can be expected from the multiselector. Now, in the time required for the establishment or the removal of a connection, the connecting and selecting .magnet operating time can be very small relative to the time necessary for the selecting finger to be damped sufliciently.

An object of the invention is to solve this vibration problem by utilizing a new type of selecting finger which does not present any amplitude vibration resulting in an untimely connection.

A further object of the invention is to provide a selecting finger constituted by a flexible wire integral at one of its extremities with a plate or similar device and bearing on each side of the wire axis. The assembly formed by the wire and the plate is held by a prestretched elastic device whose force direction coincides with the wire axis in order to hold the assembly at rest against its bearings.

3,225,518 Patented Dec. 28, 1965 Yet another object of this invention is to provide a selecting bar that includes two articulation edges and selecting fingers comprising two dihedrals. The selecting fingers bear on the articulation edges engaged at the bottom of the dihedrals. The edge profile as well as the dihedral angle being appropriately determined in order to permit the articulation of the selecting finger-plate system, around one or other of the edges.

A feature of the invention relates to a selecting finger associated with a U shaped selecting-bar, the selecting finger plate taking its bearing on the extremities of the U arms, the elastic device being fastened to the bar and to the plate,

Another feature of the invention is that for each selecting finger, the selecting bar presents a part suitably cut in order to receive the selecting finger plate and prevents any longitudinal displacement of said selecting finger.

According to an alternative embodiment another feature of the invention is that the selecting finger plate includes two articulation edges, said edges respectively taking their bearings on the bottom of the two dihedrals provided on the selecting bar.

According to this alternative embodiment another feature of the invention is that each dihedral comprises a part out out in each U arm of the selecting bar; said part being afterwards properly bent.

Another feature of the invention is that the small side of the selecting finger plate is less than the internal width of the bar, which enables the insertion or the withdrawal of the plate inside the bar, in order to permit easy mounting or removal of the selecting finger.

Another feature of the invention is the choice of the spring tension so that the torque produced is equal or superior to the torque due to the selecting finger inertiae, when the selecting bar moves from one position to an other (put in selection position or restored to rest position), in order that, with respect to the bar, the selecting finger remains at any time at rest if it is not held by a holding armature in connection position.

Another feature of the invention relates to the fact of choosing the position of the center of inertia working center of the selecting finger, taking into account the distance between the two articulation edges, so that the selecting finger, released from a connection position and restored to zero position consequential to the spring force cannot, after having overstepped its rest position, engage a second selection position in the opposite direction.

Various further features will be disclosed from the following description which is given by way of non-limited example, and with reference to the accompanying drawings wherein:

FIGURE 1 represents a cross-section view of selecting finger associated with a selecting bar according to the invention;

FIGURE 2 represents a perspective View of the select ing bar used in the device of FIGURE 1;

FIGURE 3 represents a perspective view of the selecting finger plate utilized in the device of FIGURE 1; and

FTGURES 4, 5 and 6 represent three views similar to the preceding ones but relating to another embodiment of the invention.

FIGURES 1, 2 and 3 cover the same embodiment. FIGURE 1 shows a cross-sectional view of a selecting finger including a slightly flexible steel wire f, a helical spring 1' and a plate 2. The latter is firmly fixed to wire f. It can be in plastic, in metal, or include a metallic cylinder, in copper for example, traversed by the steel wire and pinched on it, and a molded piece of nylon for example, the coppcr cylinder being riveted on the nylon piece.

The U selecting bar referenced by s, presents two edges x and y against which plate p leans. The spring r is previously stretched. The spring tension is sufficient to maintain the selecting finger in the position shown with respect to the bar, when the latter is operated.

It can be seen that the bar internal edges serve as articulation edges, the plate presenting an obtuse dihedral opposite each edge.

In fact, edges x and y may present any angle provided that the dihedrals presented by the plate be superior, in order that the latter pivots, in both directions only on these edges.

When the selecting finger is in operating position, it is held by its extremity e in the position represented by a dash-dot line. It is then leaning against edge x. When the selecting finger is not connected it returns to its initial position without its overstepping causing any disturbance.

FIGURE 2 illustrates a perspective view of the selecting bar and, more particularly, the fastening point of a selecting finger. It can be seen that both edges x and y are located at the bottom votnotches d in order that the selecting finger cannot move longitudinally. These notches can be a little wider at the upper part than at the bottom in order to facilitate the selecting finger insertion.

FIGURE 3 illustrates a perspective view of the selecting finger plate and more particularly shows that the plate is rectangular and that the small side is shorter than the internal width of the bar. This enhances the mounting or removal of a selecting finger.

FIGURES 4, 5, 6 similarly describe another embodiment of the invention. The principle is the same, but the selecting finger articulation is an edge of the plate. For this purposes, notches d are made by metal bulging, to form a practically rectangular dihedral receiving plate edge.

It is obvious that a selecting bar, like that of FIGURE 5, could be used with the selecting finger of FIGURE 3.

The operation of these devices is the same. First, assume that the selecting bar s undergoes rotation around axis 0-0 (FIGURE 2) for example when the bar is in selection position. In order that the selecting fingers remain at rest, with respect to the bar, it suffices that the force exerted by spring 1' be superior to the interia force exerted on the selecting fingers. This is valid when the bar returns to its initial position, except for one of the selecting fingers which remains held in the connection position by means of a holding armature. The latter, for instance, occupies the position roughly indicated by the dash-dot line of FIGURE 1.

When the call thus established is over, the holding armature is released as well as the selecting finger. It is restored to initial position by spring r. The selecting finger pivots on edge x and, when it reaches rest position, it strikes against edge y and rebounds, overstepping the rest position according to the mass distribution and the geometry of the whole device. A judicious choice of the elements constituting the selecting finger and of the dimensions involved obviates the possibility of the selecting 4 finger overstepping its rest position and engaging the selection position opposite to the one it has just left.

While the principles of the invention have been described above in connection with specific apparatus, it is to be clearly understood'that this description is made only by way of example and not as a limitation on the scope of the invention. '1

What is claimed is:

I. A selecting finger arrangement for crossbar switches having selecting bars, selecting wires associated with said selecting bars, mounting assembly means for mounting said wires on the associated selecting bars, said mounting assembly means comprising plate means, means for attaching said plate means to said wires so that said plate means is integral to said wires at the extremities of said wires that are proximate to said selecting bars, and means for pretensioning said mounting assembly means to cause said plate means to abut against said selecting bars whereby said mounting assembly means acts to dampen any vibrations in said wires.

2. In the selecting finger arrangement of claim 1 wherein said pretensioning means comprises helical spring means having a force direction that coincides with the axis of said wires.

3. In the arrangement of claim I wherein said selecting bars comprises two articulation edges, said plate means comprises two dihedrals, and said plate means engages and bears on the articulation edges at the bottom of the dihedrals.

4. In the selecting finger arrangement of claim 1 wherein said selecting bars are U shaped, said plate means bearing on the edges of the U arms and said pretensioning means are fastened to said plate means and to said selecting bars.

5. In the selecting finger arrangement of claim I wherein said selecting bars comprise means for receiving said plate means and for preventing longitudinal displacement of said mounting assembly means.

6. In the selecting finger arrangement of claim 1 wherein said plate means comprises two articulation edges, said selecting bars comprise two dihedrals and said edges bear on the bottom of said dihedrals.

7. In the selecting spring arrangement of claim 6 wherein said selecting bars are U shaped and said dihedals comprise a part of said selecting bars slotted and bent.

8. In the selecting finger arrangement of claim 7 wherein said plate means is smaller than the internal width of said selecting bars.

References Cited by the Examiner UNITED STATES PATENTS 1,013,410 1/1912 Lynch 2671 2,943,170 6/1960 Vradenburgh 200-166 X 3,014,103 12/1961 Moran et a1 200166 X 3,033,965 5/1962 Wolak et al. 200166 KATHLEEN H. CLAFFY, Primary Examiner.

BERNARD A. GILHEANY, Examiner. 

1. AN SELECTING FINGER ARRANGEMENT FOR CROSSBAR SWITCHES HAVING SELECTING BARS, SECTING WIRES ASSOCIATED WITH SAID SELECTING BARS, MOUNTING ASSEMBLY MEANS FOR MOUNTING SAID WIRES ON THE ASSOCIATED SELECTING BARS, SAID MOUNTING ASSEMBLY MEANS COMPRISING PLATE MEANS, MEANS, FOR ATTACHING SAID PLATE MEANS TO SAID WIRES SO THAT SAID PLATE MEANS TO INTEGRAL TO SAID WIRES AT THE EXTREMITIES OF SAID 